1. Field of the Invention
The present invention relates to production of slide fasteners, and more particularly to a method of and apparatus for attaching top stops of synthetic resin to a continuous slide fastener chain.
2. Description of the Prior Art
In the manufacture of slide fasteners, it is known to form a pair of top stops from a synthetic resin film placed on the upper surface of a continuous slide fastener chain and to attach the top stop thereto simultaneously with the forming of the top stops. For this purpose it is known to use a so-called ultrasonic or high-frequency horn which melts the synthetic resin film and shapes the melted synthetic resin into the top stops. As a result the top stops are fused with the respective tape surfaces of the slide fastener chain. However, with this conventional attaching method, it is difficult to attach the top stops to the tape surfaces with adequate firmness. Further, since the tapes of the slide fastener chain are woven or knitted and hence have rough surfaces, burrs would be formed on the top stops while the latter is being shaped.
To this end, a solution has been proposed in which U-shaped top stops are provided from an elongated flat strip of synthetic resin or from an elongated strip of U-shaped cross section, are then placed astride of the respective inner edges of the opposed tapes, are finally fused, by means of an ultrasonic horn, at only inner surface layers of each top stop which are in contact with the tape surfaces. However, this prior method is not automatic and is hence inefficient.